ODBC SQL question

Hi

I'm running PostgreSQL v6.4.2 on Red Hat Linux 6.0. I use it on a Windows NT
server 4.0 with service pack 5 through ODBC calls; the ODBC driver is the
one from Insight Distributions System, v6.40.00.06.

Usually everything is fine. My datasource works, as I can link tables from
MS Access 97 without problems.

Here is what I don't understand:
Query1: SELECT * FROM sites WHERE free = FALSE;
Query2: SELECT * FROM sites WHERE free IS FALSE;

When I run them within psql, both queries output the requested rows.

Through the ODBC driver, query1 complains that "ERROR: There is more one
possible operator '=' for types 'bool' and 'int4' You will have to retype
this query using an explicit cast (#1)

query2 complains for "Invalid use of Is operator in query expression 'free
IS FALSE'"

I tried fiddling with the ODBC driver parameters, to no avail. What do I do
wrong? I ran the queries with MS Access 97 and also with pgAdmin 6.4.3 beta,
they both return the same errors. Anybody could help me?

Here is the table definition:
+---------------------+--------------+-------+
| Field | Type | Length|
+---------------------+--------------+-------+
| site_id | int4 | 4 |
| name | varchar() | 50 |
| ip | varchar() | 15 |
| parent | int4 | 4 |
| type | int4 | 4 |
| owner | int4 | 4 |
| admin | int4 | 4 |
| creation_date | datetime | 8 |
| non_profit | bool | 1 |
| free | bool | 1 |
| reg_fee | bool | 1 |
| bill_period | int2 | 2 |
| bill_date | datetime | 8 |
| bill_paid | bool | 1 |
| paid_until | datetime | 8 |
| size | int4 | 4 |
| peek | int4 | 4 |
| list_personal | bool | 1 |
| list_organisation | bool | 1 |
| list_business | bool | 1 |
| title_fr | varchar() | 75 |
| title_en | varchar() | 50 |
| description_fr | varchar() | 254 |
| description_en | varchar() | 254 |
| free2 | bool | 1 |
+---------------------+--------------+-------+

Accept my apologies if I'm not in the right place to ask this. If this is
the case, please tell me where I should direct my question.

Thanks,

Nicolas Cadou